A combined cycle power plant using a gas turbine has a high heat efficiency in comparison with a thermal power plant using a coal-fired boiler, and the amount of SOx and soot and dust generated from the combined cycle power plant is small since it uses natural gas mainly as fuel, and therefore, the burden on exhaust gas purification is small, whereby the combined cycle power plant has gained attention as a power plant with great future potential. Furthermore, the combined cycle power plant is excellent in load responsibility, and has gained attention simultaneously as a power generation method which can rapidly change its power output in accordance with power demands, suitable for high-frequency start and stop (daily start and daily stop).
The combined cycle power plant comprises main components including an HRSG for generating steam by using a power generating gas turbine and exhaust gas from the gas turbine and a steam turbine for generating power by using steam obtained by the HRSG.
FIG. 1 is a schematic block diagram of a horizontal HRSG having a supporting burner inside, wherein the HRSG has a casing 1 that is a gas duct in which exhaust gas G from the gas turbine flows horizontally, the supporting burner 2 is disposed at the inside of the casing 1 at an inlet of the gas turbine exhaust gas G, and at the downstream side thereof, a heat exchanger tube bundle 3 is provided. The heat exchanger tube bundle 3 is generally provided with, in order from the upstream side to the downstream side, a super heater 3a, an evaporator 3b, and an economizer 3c, and in some cases, provided with a reheater (not shown).
Equipment including the HRSG that compose the combined cycle power plant have small capacities in comparison with equipment composing a high-capacity thermal power plant, and can be transported after being assembled up to a stage close to completion within a plant equipment manufacturing factory, and in this case, installation on site is comparatively easy. Therefore, installation is completed in a short period in comparison with high-capacity equipment composing the thermal power plant.
However, even under these circumstances, the HRSG is not small in size, and its installation requires enormous labor and time. For example, for conventional installation of an HRSG, a bundle 3 of a necessary number of heat exchanger tubes each of which includes one hundred and several tens of heat exchanger tubes and headers as one unit are transported to a construction site, and heat exchanger tube panels are suspended for each unit from support beams provided on the ceiling of the HRSG casing constructed in advance at a construction site. Such work of suspending thousands or ten of thousands of heat exchanger tubes at a high place is not only dangerous but also results in an extended work period and high construction costs.
Therefore, a technical development has been strongly demanded which makes the construction of an HRSG easy by dividing the heat exchanger tube bundle 3 of the HRSG into several modules and modularizing the equipment composing the HRSG so that the modules are completed as one unit within a manufacturing factory and installation is completed by only assembling the unit.
Particularly, considering the circumstances that supply of HRSG construction parts and securing of experienced construction personnel outside Japan are difficult, the modularization method is very advantageous in which, within a domestic equipment manufacturing factory having a technical capacity necessary for manufacturing equipment composing an HRSG, a full management system for quality control or process management, etc., and a large number of skilled personnel, the equipment is completed as part products divided into a plurality of modules, transported to the site and assembled. Particularly, development of a method in which an HRSG whose capacity is comparatively great among equipment composing a combined cycle power plant is manufactured as a plurality of divided modules in advance in a factory and the modules are assembled at the HRSG construction site has been demanded.
An object of the invention is to provide an advantageous HRSG construction method in which components of an exhaust heat recovery boiler are manufactured and divided into a plurality of modules in a factory and then the modules are transported to the site and assembled, wherein heat exchanger tube panel modules are employed in this method.
Another object of the invention is to provide an HRSG construction method which prevents heat exchanger tube panels from being damaged during transportation, reduces transportation costs simultaneously, and reduces members to be wasted after installation, and heat exchanger tube modules to be used in this method.